Rotor assembly



Jan. 12, 1965 B. J. ANDERSON 3,165,294

ROTOR ASSEMBLY Filed Dec. 28, 1962 United States Patent I Thisinvention'relates to rotor assemblies for fluid flow machines such ascompressors and, more particularly,

to a locking arrangement for holding the blading of such machines inassembled position.

There are two main types of conventional rotor assemblies. The firsttype of conventional rotor structure isthe built-up or disc. typecomprised of a plurality of 1 elements axially bolted or otherwisesecured together to'form an integral structure. In this type of rotorassembly, it is generally not possible to remove individual bladeswithout disassembling the entire rotor since the blades are generallyheld in axially extending dovetail slots in the periphery of the disc.The second type of conventional rotor assembly is the drum type rotorassembly such as shown by United States Patent No. 2,931,625 toLechthaler et al., issued April 5, 1960, and assigned to the assignee ofthis application. In the drum type rotor assembly the blades aregenerally vheld in circumferentially extending dovetail slots and may'be" inserted or removed without disassembling the entire rotor. Inaddition to permitting easy insertion and removal of rotorblades, thedrum type rotor assembly is relatively] lightweight. in combination withadequate strength makes the drum type rotor assembly particularly suitedfor use in gas turbine engines'used for aircraft propulsion. Thepresent.

proved rotor assembly in which, none: of the blades or blade roots areof special design or shape.

A still further object of this invention to to provide a rotor assembly'in which theblades of a given stage are consecutively positioned, theentire row of blades then being locked into position without additionalmove-v ment of the blades being required.

An additional object is to provide an improved rotor assembly notrequiring the use of complicated or unusual locking devices or tools.

Yet another object of this invention to to provide a rotor assemblywhich is simple and inexpensive 'to assemble, disassemble, service andmanufacture, but yet is rugged and durable and requires a minimum ofmaintenance. 1 I 1 I Briefly stated, in accordance with the illustratedembodiment of the invention, a rotor drum is' provided withcircumferentially continuous walls defining 'a dovetail slot in theperiphery thereof. A loading recess is provided in the radially "inwardsurface of the slot. A plurality of identically shaped dovetail rotorblade roots are consecutively inserted intozthe dovetail slotatthe.

loading recess and then moved circumferentially into abuttingrelationshipwithin the slot, the dovetail shapes of the slot andtheblade roots preventing radial movement of the blade roots relative tothe rotor drum. The

The light weight construction the loading recess.

which:

arsenal Patented Jan. 12, 1965 ice last blade root inserted ispositioned radially outward of A locking means engages the last bladeroot to hold it in the dovetail slot and to prevent circumferentialmovement of the blade roots within the slot.

While the invention is distinctly claimed and particularly pointed outin the claims appended hereto, the invention, both as to organizationand content, will be better understood and appreciated, along with otherobjects and features hereof, from the following detailed descriptiontaken in conjunction with the drawing, in

FIGURE his a partial cross sectional view of a drum type rotor assemblyconstructed in accordance with this invention;

FIGURE 2 is a perspective view of a portion of the rotor assembly ofFIGURE 1 showing one of the dovetail slots and its associated loadingrecess;

"FIGURE 3 is a view in cross section ofthe dovetail slot of FIGURE 2illustrating in addition one of the rotor blades in its loading positionand the locking means in its unlocked position;

FIGURE 4 is a view similar to FIGURE 3 showing the locking bladepositioned in the dovetail slot and the locking means in its lockedposition;

- FIGURE 5 is a perspective view of the rotor blade shown in FIGURE 3;and

FIGURE 6 is a perspective view similar to FIGURE 5 showing the lockingblade of FIGURE 4 in detail.

Referring first to FIGURE 1, a generally cylindrical blade holdingmember or rotor drum 10 is partially illustrated, the drum 10 havinginwardly extending radial flanges 11 and 12 at its ends. The flanges 11and 12 are secured by suitable fastening means, such as a plurality ofcircumferentially spaced bolt connections 13, to flanges 14 and 15,respectively. To increase the rigidity of the rotor drum construction,the flanges 14 and 15 are connected by a plurality'of circumferentiallyspaced axial tie bolts 16. The flanges 14 and 15 are connected to shaftportions (not shown) to form a complete rotor' assembly, the shaftportions being suitably mounted in bearings (not shown) to support andpermit rotation of the rotor assembly; As this description proceeds, itwill become obvious to those skilled in the art that the structuredescribed above may be changed or modified'substantially withoutdeparting from the true spirit and scope of the invention, which willnow be described.

The rotor drum 10 is provided with a plurality of axial spacedcircumferentially extending slots 20, one of the slots-20 being shown ingreater detail by FIGURES 24.

. As shown by FIGURES 24, the slot '28, which may be of the dovetailslot 20, the recess 23 having its deepest point adjacent slot side wall21 so that the recess 23 essentially forms a radially inwardcontinuation of the side wall 21. A radially extending threaded ortapped hole 25 is provided adjacent the loading recess 23, a threadedmember of plug 26 being received therein. As shown by FIGURE 4, the head28 of the threaded plug 26 is provided with a recess 29 for receiving atool such as, for example, an Allen wrench for screwing the threadedplug 26 into and out of the tapped hole 25 between the extreme positionsshown by FIGURES 3 and 4.

Returning briefly to FIGURE 1, it will be seen that a circumferentialrow of blades 32 is supported from each of the dovetail slots 20. Themanner in which these blades 32 are positioned, supported, and lockedinposi- A loadtion will now be described in detail. One of the blades 32is illustrated by FIGURE 5, the blade having a root. j

portion 33 of dovetail configuration. side walls 3 1,- and 35 inclinedso as to form leading and trailing toe portions 36 and 3'7,respectively. .The dovetail configurations of the slot 29 and the root33 are the.

same with the. root 33 being sufiiciently smaller in size than the slot29 to be slidably received therein, the fit between the root 33 and theslot 24) being as snug as practicable.

Referring now to FEGURE 3, the threaded plug 26 isscrewed into thetapped hole 25 to the position shown and then a first one of the blades32 and its associated The root 33 has root 33 is tipped intothe positionshown by solid lines, a

the leading'toe 36 of the root 33 extending into the recess 23. With theleading toe 36extending into the recess 23, the trailing toe 37 can bemoved radially into the slot 29. The blade 32 and its associatedroot 33may then be tipped into the position shown by dotted lines and movedcircumferentially in the dovetail slot 2tl to a desired position. Withthe root 33 and the slot 2tl having the same dovetail configuration anda snug fit, the blade 32 is restrained against radial movement withrespect to the'drumlt). Other blade roots may be posi tioned in asimilar fashion. At this point it will not only be obvious that thecircumferentialextentof therecess 23 must be sufficient to receive theroots 33, but also be; obvious that the circumferential extent should beno greater than required in order to restrain the maximum number ofblades against radial movement. Therefore,

it can be stated that the circumferential extentof. the recess 23 issufficient to receiveonly one of the root portions 33.

The entire circumferentially extending dovetail slot can be filled withblade roots 33 in the manner described: above, the roots 33 beinginserted into the slot 20 at the loading recess 23 and then being movedcircumferentially into abutting relationship. The last blade rootinserted, however, fills the space in thedovetail slot 2tl radiallyoutward of the loading recess23 and is not moved cir-' curnfer entiallywithin, the slot'2tl. This last blade is not heldagainst radial movementrelative to therotor drum 10 solely by the dovetail configuration of theslot 20 since the circumferential extent of the recess 23 is necessarily greater than that of the last blade root in order to permitinsertion of the blade roots 33 into the dovetail slot 20. Locking meansmust be provided for holding;

the last blade or locking blade in the slot 20. To effectively lock the,last blade against radial movement relative to therotor drum 10, aslightly modified structure is used for the last or locking blade 32A asillustrated by FIG- URES 4 and 6. Referring first to FIGURE 6,;blade32Ais identical to blades 32 and has a root 33A identical in dovetail shapeto roots 33. The onlyidilference between;

the roots 33 and 'the root 33A is that an access passage 4% is providedthrough the root 33A. Passage 40 is provided with a counterbore 41 asbestshown'by FIG- URE 4.

The root 33A of the locking blade 32A is inserted into the dovetail slot2! in the same manner as roots 33 and then is positioned in the dovetailslot 20 as shown by FIG-,

URE 4,the access passage 4t) being radially aligned with thethreadedplug 26 which comprises the locking means.

With the'root 33A positioned in the slot 20, a suitable tool is insertedthrough the passage 46) into the cavity 29 in the threaded plug 26 toscrew the plug 26 outwardly into the locking position shown by FIGURE:4. The counterbored portion 41 of the passage 40 issufiiciently large toreceive the head 28 of the plug 26, the remainder screwing the plug 26into the tapped 21 and 22 of the dovetail slot 20 are continuous withnointerruptions therein.- This means that each of-the blade roots,including root 33A; of the locking blade 32A, is

restrained against radial movementwith respect to the rotor drum 10across the entire wall surfaces34 and 35, or 34A and 35A, of the root.As a result, the relatively shallow dovetail slot 20 may beutilizedsince there is no weak area in which a deeper slot must be utilized togain sufiicient strength. The means, in,turn,'that therelatively thinwalled rotor drum 10 can be used to provide a lighter Weight. structurethan heretofore possible. Also, the

root 33A difiers from roots 33 only in that an access passage 40 isprovided therein. Since a dovetail of special or unusual form is thusnotrequired for the locking blade 32A, a more economical and 'uniformrotorassembly results. In addition, there is no requirement that theentire row of bladesbe movedbircumfereritiali as a unit at any time. 7 Aassembly anddisassembly,

' It will be understood that the invention isnot limited to the specificdetails of 'construction'and arrangement ofthe embodiment illustratedand described herein since changes and modificationswill be obvious: tothose skilled in the art For example, the dovetailslots-Ztl may beprovided in the periphery of a disc type rotor assembly instead of inthe rotor drum 10 of a drum type assembly. Also,'it may, bedesirable onoccasion to eliminate the access passage/i0 in the root 33Aiandoperatethe locking means from within the interior of the rotor drum 10.It

is therefore intended to cover in the appended'claims all such changesand modifications which mayoccurto those skilledvin the art withoutdeparting from the true spirit and scope of the invention. What isclaimed as new and desired to Patent of the United Statesis: a a Y 1. Abladed rotor assembly for anraxial fluid flow secure by Letters vmachine comprisingagenerally cylindrical blade holding member, saidblade holding member-having circumferent ally continuous Walls definingat least one circumferentially extending;dovetail shaped slot in theperiphery thereof, a plurality of blades all having identicallyshapeddovetail roots slidably received in said slot, said blade rootscircumferentially filling said slot with adjacent roots .in abuttingrelationship, the dovetail shapes of said slot and said blade rootsbeing such that the roots are restrained against radial movement Withrespect to said blade holding member, a loading recess in the radiallyinward surface of the slot, a selected one :of said blade rootspositioned in said slot'radially outward of said loading recess,,an dlocking means engaging the radially inward portion'of said selected.blade root'to'. maintain said selected blade root in said slot and toprevent circumferentialmovement of said plurality 'oflblade'roots insaid slot. I

' .2. A bladed rotor assembly as defined in claim 1 inwhich.thewcircumferential extent of said loading recess is sufiicient toreceive only one of said blade roots. 7

of the passage 40 being smaller in diameter than the head 28. With thehead-28 of the plug 26 received in the.

counterbored portion 41 of the passage40, the blade 32A is held againstradial movement relative to the rotor drum 10. It will be obvious thatthe threaded plug 26v also 3. A bladed rotor assembly for, an axialfluidflow 'machine comprising a generally cylindricalbladeholdingmember, said blade holding member having circumferentially continuouswalls defining at. least one circumferentially extending dovetail'shapedslot in the'periphery thereof, a plurality of blades all-havingidentically shaped This obviously. 'greatlyincreases ease of I dovetailroots slidably received in said slot, said blade 1 ried by said bladeholding member, a selected one of said blade roots positioned in saidslot radially outward of said loading recess, said locking means beingmovable radially outwardly to engage said selected blade root so as tomaintain said selected blade root in said slot and to preventcircumferential movement of said plurality of blade roots in said slotand movable radially inwardly so as to'permit insertion and removal ofsaid blade roots into and from said slot.

4. A bladed rotor assembly for an axial fluid flow machine comprising agenerally cylindrical blade holding member, said blade holding memberhaving circumferentially continuous walls defining at least onecircumferentially extending dovetail shaped slot in the peripherythereof, a plurality of blades all having identically shaped dovetailedroots slidably received in said slot, said blade roots circumferentiallyfilling said slot with adjacent roots in abutting relationship, thedovetail shapes of said slot and said blade roots being such that theroots are restrained against radial movement with respect to said bladeholding member, a loading recess in the radially inward surface of saidslot, the circumferential extent of said loading recess being sufiicientto receive only one of said blade roots, and radially movable lockingmeans comprising a threaded member rotatably received in a radiallyextending threaded hole in the radially inward surface of said slot, aselected one of said blade roots positioned in said slot radiallyoutward of both said loading recess and said threaded member, saidthreaded member being movable radially outwardly to engage said selectedblade root so as to maintain said selected blade root in said slot andto prevent circumferential movement of said plurality of blade roots insaid slot and movable radially inwardly so as to permit insertion andremoval 'of said blade roots into and from said slot.

5. A bladed rotor assembly as defined in claim 4 in which said selectedblade root has a passage extending therethrough for providing access tosaid threaded memher.

6. A bladed rotor assembly as defined in claim 5, said passage radiallyaligned with said threaded member, and the radially inward portion ofsaid passage counterbored, said threaded member extending into saidcounterbored portion when said threaded member is in its radiallyoutward position.

6 7. A bladed rotor assembly for an axial fluid flow machine comprisinga thin walled cylindrical drum, said cylindrical drum havingcircumferentially continuous walls defining a plurality of shallowaxially spaced circumferentially extending dovetail shaped slots in theperiphery thereof, a plurality of blades all having identically shapeddovetail roots slidably received in each of said slots, said blade rootscircumferentially filling each of said slots with adjacent roots inabutting relationship, the dovetail shapes of said slots and said bladeroots being such that the roots are restrained against radial movementwith respect to said drum, a loading recess in the radially inwardsurface of each of said slots, the circumferential extent or" each ofsaid loading recesses being suflicient to receive only one of said bladeroots, and radially movable locking means associated with each of saidslots comprising a threaded member rotatably received in a radiallyextending threaded hole in the radially inward surface of each of saidslots, a selected one of said blade roots in each of said slotspositioned radially outwardly of the respective loading recess andthreaded members, said threaded members being movable radially outwardlyto engage the associated selected blade root so as to maintain saidselected blade root in said slot and to prevent circumferential movementof said plurality of blade roots in said slot and movable radiallyinwardly so as to permit insertion and removal of said blade roots intoand from said slot.

8. A bladed rotor assembly as defined in claim 7 in which each of saidselected blade roots has a passage extending therethrough for providingaccess to the associated threaded member, said passage radially alignedwith said threaded member, and the radially inward portion of saidpassage counterbored, said threaded member extending into saidcounterbored portion when said threaded member is in its radiallyoutward position.

References Cited by the Examiner UNITED STATES PATENTS 886,515 5/08 Jude253-7 2,315,631 4/43 Lloyd 25377 2,918,255 12/59 McGinnis 25 37 72,931,625 4/60 Lechthaler et al 25 3-77 3,088,708 5/ 63 Feinberg 25377FOREIGN PATENTS 23,387 1910 Great Britain. 659,592 10/51 Great Britain.704,882 3/54 Great Britain. 409,564 2/45 Italy.

JOSEPH H. BRANSON, 111., Primary Examiner.

1. A BLADED ROTOR ASSEMBLY FOR AN AXIAL FLUID FLOW MACHINE COMPRISING AGENERALLY CYLINDRICAL BLADE HOLDING MEMBER, SAID BLADE HOLDING MEMBERHAVING CIRCUMFERERTIALLY CONTINUOUS WALLS DEFINING AT LEAST ONECIRCUMFERENTIALLY EXTENDING DOVETAIL SHAPED SLOT IN THE PERIPHERYTHEREOF, A PLURALITY OF BLADES ALL HAVING IDENTICALLY SHAPED DOVETAILROOTS SLIDABLY RECEIVED IN SAID SLOT, SAID BLADE ROOTS CIRCUMFERENTIALLYFILLING SAID SLOT WITH ADJACENT ROOTS IN ABUTTING RELATIONSHIP, THEDOVETAIL SHAPES OF SAID SLOT AND SAID BLADE ROOTS BEING SUCH THAT THEROOTS ARE RESTRAINED AGAINST RADIAL MOVEMENT WITH RESPECT TO SAID BLADEHOLDING MEMBER, A LOADING RECESS IN THE RADIALLY INWARD SURFACE OF THESLOT, A SELECTED ONE OF SAID BLADE ROOTS POSITIONED IN SAID SLOTRADIALLY OUTWARD OF SAID LOADING RECESS, AND LOCKING MEANS ENGAGING THERADIALLY INWARD PORTION OF SAID SELECTED BLADE ROOT TO MAINTAIN SAIDSELECTED BLADE ROOT IN SAID SLOT AND TO PREVENT CIRCUMFERENTIAL MOVEMENTOF SAID PLURALITY OF BLADE ROOTS IN SAID SLOT.